In recent years, a plurality of methods in which a 3D printer is used to produce a shaped article have been proposed. In particular, ink-jet stereolithography using an ink-jet technology, which is realized by a 3D printer, is known. Ink-jet stereolithography is a method in which curable ink ejected from an ink-jet head is cured through irradiation with light such as ultraviolet rays or the like and layered, and a shaped article is thereby produced. The ink-jet stereolithography is suitable for producing a shaped article that is required to be accurately formed because layers are formed by ejecting minute droplets of curable ink, and thus a highly accurate shaped article with smooth surface can be obtained.
In ink-jet stereolithography, the formation of a three-dimensional shaped article starts from the bottom surface portion, and therefore, ink for a model material for forming a shaped article and ink for a support material for supporting the shape of a shaped article during its production are used as the curable ink in order to produce a three-dimensional article having a shape that is difficult to shape as it is, such as an eave shape. A support material (support material cured article) that is a cured article of this ink for a support material is ultimately removed, and the final shaped article made of the ink for a model material is thus obtained. An example of a method for removing the support material is a method in which the support material is dissolved in water and then removed. For example, Patent Document 1 proposes a support material containing a water-soluble monofunctional ethylenic unsaturated monomer, an alkylene oxide adduct having an oxypropylene group, and a photopolymerization initiator.
When the amount of the alkylene oxide adduct having an oxypropylene group, which has excellent water solubility, contained in the support material described in Patent Document 1 is greater than or equal to a certain amount, water solubility can be imparted to a polymer of the water-soluble monofunctional ethylenic unsaturated monomer polymerized through irradiation with ultraviolet rays, thus making it possible to remove the support material with water.